Why Oklahoma Is Seeing More Earthquakes

Lately, Oklahomans are as wary of earthquakes as tornadoes.

— -- Lately, Oklahomans are as wary of earthquakes as tornadoes.

The Midwest as a whole has seen a spike in powerful quakes in recent years, which scientists say is linked to fracking.

The United States Geological Survey recorded 1,010 earthquakes of a magnitude 3.0 or greater in the region last year, a nearly three-fold increase from the 318 temblors of this magnitude in 2009. Oklahoma alone felt 619 quakes of a magnitude 2.8 or larger from January through June of this year.

The increase of high-magnitude earthquakes in the region has been tied to the surge in oil and gas operators’ use of hydraulic fracturing, or fracking, in which water, sand and chemicals are injected at high pressures into the earth to release oil and gas trapped inside the rock.

Last month, the Oklahoma Geological Survey began a six-month study of oil and gas injection wells to better understand quakes triggered by this technique, Public Radio Tulsa reported.

Officials in Oklahoma are still assessing the aftermath of Saturday morning’s 5.6 magnitude earthquake, one of the largest quakes on record in the state. An earthquake of the same magnitude rattled the region in November 2011.

The latest quake happened at 7:02 a.m. local time in north-central Oklahoma and was felt in other parts of the Midwest, from Nebraska to north Texas. Its epicenter was about 9 miles northwest of the town of Pawnee and some 73 miles northeast of Oklahoma City.

Police in Pawnee said windows were shattered and the facades of some brick buildings were damaged.

ABC News’ Matthew Fuhrman and Matt Foster contributed to this report. The Associated Press also contributed to this report.